In an existing Long Term Evolution (LTE for short) system, a length of a subframe is 1 ms, and a length of a transmission time interval (TTI for short) is set to 1 ms. All scheduling in the LTE system is performed by using the TTI as a minimum scheduling unit. Currently, to make a data transmission delay shorter, a scenario in which the length of the TTI is set to 0.5 ms or less than 0.5 ms is proposed, to shorten a round trip time (RTT for short), so as to shorten a data transmission delay. FIG. 1 to FIG. 4 are schematic sending diagrams of some physical channels in frequency division duplex (FDD for short) of an LTE system in the prior art. Referring to FIG. 1, an uplink and a downlink are borne on different carriers, a physical downlink control channel (PDCCH for short) schedules transmission on a physical downlink shared channel (PDSCH for short) and a physical uplink shared channel (PUSCH for short). A physical uplink control channel (PUCCH for short) may be configured to bear feedback information of the PDSCH, that is, a network is notified of whether UE correctly receives data borne on the PDSCH. A physical HARQ indicator channel (PHICH for short) is configured to bear feedback information of the PUSCH, that is, the network notifies the user equipment (UE for short) of whether information sent by the PUSCH is correctly received. A relationship between a channel data part and a demodulation reference signal (DMRS for short) of the PUSCH is shown in FIG. 2. A relationship between a channel data part and a DMRS of the PUCCH is shown in FIG. 3.
However, when an existing DMRS transmission mechanism is applied to some scenarios, the mechanism cannot meet a requirement for performing frequency offset estimation by a base station. For example, when sending is performed by using a TTI whose length is 0.5 ms or less than 0.5 ms, the PUSCH is shortened to one timeslot, (while currently, one PUSCH generally has two timeslots) and an original timeslot structure of the PUSCH remains unchanged. Referring to FIG. 4, in this case, only a DMRS of one symbol is left in one timeslot in the prior art. However, when the frequency offset estimation is performed, DMRSs of at least two symbols are required to ensure accuracy of the frequency offset estimation. Therefore, in the prior art, when sending is performed by using a TTI whose length is 0.5 ms or less than 0.5 ms, accuracy of frequency offset estimation is reduced. For another example, when a high-speed railway user uses an existing LTE technology, a high speed causes a relatively large Doppler shift. However, the base station is based on the existing DMRS transmission mechanism in which a high-speed movement factor is not considered, so that accuracy of the frequency offset estimation is reduced.
To sum up, by means of the existing DMRS transmission mechanism, accuracy of the frequency offset estimation performed by the base station is reduced.